In the semiconductor manufacturing industry, photoresist materials are used for transferring an image to one or more underlying layers, such as metal, semiconductor and dielectric layers, disposed on a semiconductor substrate, as well as to the substrate itself. To increase the integration density of semiconductor devices and allow for the formation of structures having dimensions in the nanometer range, photoresists and photolithography processing tools having high-resolution capabilities have been and continue to be developed.
An important enabler for advanced lithographic patterning has been the introduction of antireflective coatings (ARCs). These materials absorb light at the resist/substrate interface to prevent reflection, thus reducing standing waves and thin-film interference to enable printing of patterns with vertical profiles. BARCs were originally implemented as a bilayer stack of photoresist on an organic ARC layer. Such ARCs were conventionally designed to etch faster than the overlying resist pattern to enable pattern transfer. With reductions in device geometry, however, the adoption of more complicated stacks has become necessary. For example, trilayer stacks of photoresist/silicon ARC/carbon has been used to enable pattern transfer at smaller dimensions, described, for example, in Weimer et al, Materials for and performance of multilayer lithography schemes, Proc. SPIE 6519, Advances in Resist Materials and Processing Technology XXIV, Proc. Of SPIE, Vol. 6519, 65192S (2007). In a typical process, a thin silicon ARC (Si-ARC) is initially opened with a fluorocarbon etch before switching to an oxygen-containing etch to transfer the pattern to the underlying carbon layer. This process has disadvantages including, for example, the need for numerous process steps leading to decreases in product throughput. In addition, the process is generally unstable with current SiARC formulations. In this regard, SiARCs are typically silicon oxide precursors made with sol-gel chemistry using condensation of silicon alkoxide precursors. The condensation reaction continues over time, which can result in increased molecular weight of the polymer and increased viscosity of the solution. As a result, such materials typically have a short shelf-life, on the order of a week. This leads to waste of the material if not used quickly.
There is a continuing need in the art for improved photolithographic methods which address one or more problems associated with the state of the art and which allow for the formation of fine patterns in electronic device fabrication.